In a sensor information collecting apparatus that measures fatigue deterioration of an infrastructure and accumulates data with a maintenance-free for 10 years by using a battery as a voltage source, a wired system and a wireless system are considered as means that reads data of fatigue deterioration information accumulated regularly (for example, every several years).
In the wired system, it is necessary to disassemble an apparatus having been subjected to dustproof and waterproof processing to extract data. Therefore, since the wired system deviates from the original concept of a maintenance-free apparatus, work is complicated and it would not be realistic.
Meanwhile, in the wireless system, in order to communicate with a wireless module installed in an apparatus, the wireless module is always controlled to be in a standby state and receives a read request signal of accumulated data, so that the accumulated data is controlled to be transmitted from the wireless module for the purpose of reading. In this way, the wireless module is always in the standby state, resulting in a problem that power consumption of a battery is large and thus the lifetime of the battery, which has been made maintenance free for 10 years, is shortened.
On the other hand, there has been disclosed a strain measuring system that reduces the consumption of a power supply unit (for example, see JP-A-2008-234361).
Paragraph 0011 of JP-A-2008-234361 discloses as the effect that “in a master unit remote from a slave unit installed in a measuring place of a measuring site, since a physical quantity generated in the measuring place of the site can be precisely grasped and a physical quantity in a place including a strain gage type sensor is measured in response to the size of the physical quantity transmitted from the slave unit previous time at a time interval determined by the master unit and is transmitted to the master unit from the slave unit, a measurement time interval is reasonably changed in response to the size of the physical quantity in the measuring site, so that it is possible to provide a strain measuring system capable of reasonably performing the reduction of the consumption of the power supply unit and the precise acquirement of accumulated data”.